This invention relates to commercial systems for washing and drying motor vehicles, such as those used in automatic car washes. More particularly, this invention relates to dryers used in motor vehicle washing and drying systems.
Several systems are known for automatically washing and drying motor vehicles. In a typical prior art system, a motor vehicle is driven onto a track which is used to mark or register one side of the vehicle. The vehicle then either remains stationary, or is moved as the washing and drying operations are performed. The location of the opposite, passenger side of the vehicle is typically determined by the washer using a contact sensor that engages the passenger side of the vehicle. The contact sensor outputs a signal indicative of the width of the vehicle, so that the washing system may adjust the proximity and/or movement of the washing brushes accordingly.
After the motor vehicle has been washed, it is typically dried by a dryer that includes one or more nozzles. The nozzles may oscillate or they may be stationary. In a typical prior art system, described in Reissue Pat. No. 33,334 issued Sep. 18, 1990, two oscillating nozzles are used to output high velocity air onto the motor vehicle. The nozzles oscillate over a wide angular range in an attempt to push the water toward the center of the vehicle and then down the front and down the rear of the vehicle. One of the nozzles is directed slightly toward the front of the vehicle, and the other nozzle is directed slightly toward the rear of the vehicle.
The vehicle dryer described in Reissue Pat. No. 33,334, as described above, has several disadvantages. First, the distance between the two opposed nozzles is not adjustable to accommodate vehicles of different sizes. Thus, the distance between the nozzles and the motor vehicle varies significantly depending upon whether a minivan, for example, is being dried or whether a small commuter-type automobile is being dried.
Another disadvantage of such prior art systems is that a significant amount of water remains on the motor vehicle after the drying cycle has finished. In such prior art systems having two nozzles, the oscillating nozzle tends to direct the water towards the central and furthermost top surfaces of the motor vehicle being dried. Since the movement of the water off the vehicle's surface is determined by the duration and momentum of the air from the nozzle, the surface areas furthest from the nozzle are not adequately dried, in part, because the air loses momentum before the air reaches the most distant surface areas.
Another reason that such prior art systems achieve incomplete drying is due to the nature of the oscillation cycles of their oscillating nozzles. In a typical prior art system, the nozzles are oscillated by air cylinders. The use of air cylinders results in oscillation cycles having a velocity profile over time that resembles a rectangular waveform. When two opposed oscillating nozzles are positioned as in Reissue Pat. No. 33,334, this velocity profile of a first nozzle causes some water to be moved to the central portion of the top vehicle surface, where the water remains until the second nozzle then pushes this water back to the place where it previously had been located, near the first nozzle. Thus, some of the water simply moves back and forth instead of being removed from the vehicle surface.
This back and forth movement of the water may be lessened to a certain degree by moving the dryer apparatus over the vehicle twice at a very slow speed, thereby substantially increasing the air's contact time with the vehicle. A substantial portion of the water will then be driven off the vehicle. However, this solution is unsatisfactory because the duration of the drying cycle is substantially increased to two or more minutes, thereby reducing the number of vehicles that can be dried in a given time period.
There are other drawbacks to prior art drying systems. For example, the typical prior art system has oscillating nozzles that oscillate at high cycle rates over wide angles of oscillation, on the theory that it is best to cover as much surface area as possible. In fact, however, the high cycle rates and wide angles of oscillation still result in significant amounts of water being left on the vehicle.
Another problem with typical prior art dryers is that the high velocity air output by the nozzles tends to lose much of its velocity and direction before the air has a chance to impinge on the more distant portions of the vehicle, such as the lower, side door panels and the central front and rear portions of the vehicle. One of the causes of this problem is that turbulent, ambient air in the dryer environment tends to diffuse the nozzle output air as the output air travels more distance from the nozzle.